1. Field of the Invention
With respect to the classification of art as established in and by the United States Patent and Trademark Office, the present invention is believed to be classified in the general class entitled "Electrical Heating" (Class 219) and in particular to the thermal cutting rods or bars used with oxygen to maintain a cutting temperature for steel, iron, concrete and the like. This bar, which sometimes is referred to as an "exothermic burning rod", includes a steel tubular shell, an interior of wire filaments and a passage through which oxygen is flowed under pressure.
2. Description of the Prior Art
A pre-examination search was conducted in the search room of the United States Patent and Trademark Office, and although the art is extensive pertaining to thermal cutting rods or bars, the concept of a thermal cutting bar or rod having the particular construction and composition described and claimed herein is believed to be novel.
In particular, there is to be noted U.S. Pat. No. 1,437,257 to Mattice, as issued in November 1921, which shows an electrode (not an exothermic burning) with a series of outer strands of steel surrounding a copper strand. U.S. Pat. No. 2,319,977 to Cape et al., as issued in May 1943, shows an electrode (not an exothermic burning rod) of ferrous alloy with a separate aluminum wire or a ferrous wire with aluminum coating. Also of note is U.S. Pat. No. 4,182,947 to Brower, as issued January 1980, and U.S. Pat. No. 4,201,902 to Rieppel, as issued May 1980.
In prior art commercially available cutting bars, a single strand of aluminum wire is employed in conjunction with a number of steel strands to provide a self-sustaining, exothermic reaction. This practice of using usually one aluminum strand isolates it and places it at best in physical contact with less than a fraction of 1% of its surface area with the adjacent steel wire components. This violates the requirement for a reaction that the components to be reacted must be in direct physical contact. The result is uneven burning with a tendency for side-wall burn, difficulty in ignition, poor thermal operating results in general, high oxygen consumption, high oxygen pressure, and large quantities of uncombined hydrogen and oxygen gases, i.e., incomplete combustion.